Electrolytic transistor



Aug. 28, 1962 J. BARDEEN 3,051,376

ELECTROLYTIC TRANSISTOR Original Filed June 2, 1953 3 Sheets-Sheet 1 ja\l ,fnunzr'. 170% Bar e en.

Aug. 28, 1962 J. BARDEEN 3,051,876

, ELECTROLYTIC TRANSISTOR Original Filed June 2, 1953 3 Sheets-Sheet 2Aug. 28, 1962 J. BARDEEN 3,051,876

ELECTROLYTIC TRANSISTOR Original Filed June 2, 1953 3 Sheets-Sheet 3 32d 34 1 O 32 c 32 Ia l I a 1 rzz/rz Z 01 Zakrz3 r 6 United States PatentOfiice 3,051,876 Patented Aug. 28, 1962 3,05ll,d76 ELECTROLYTICTRANSIFsTUR John Bardeen, Champaign, Ill, assignor to The University ofIllinois Foundation, a non-profit corporation of Illinois Continuationof application Ser. No. 359,014, June 2, 1953. This appiication May 1.4,1958, Ser. No. 735,660 2 Claims. (Cl. 317-231) This invention relates toan electroytic device and more particularly to a circuit element thatmay be termed an electrolytic transistor.

Basic research in the field of semi-conductors has culminated in thedevelopment of semi-conductor devices, generally termed transistors,with which currents can be controlled to provide amplification,oscillation and the like. See, tor example, United States Patents2,524,035 to this applicant, dated October 3, 1950 and 2,569,347 toShockley, dated September 25, 1951. The device of this invention hassome operational characteristics which are similar to those ofsemi-conductor transistor-s, particularly the so-called junctiontransistor of the Shockley patent but differs in that the medium inwhich the controlled current flow takes place is an electrolyte ratherthan a semi-conductor; this gives rise to the terminology electrolytictransistor. As will appear fully later, the electrolytic transistor hasmany characteristics which make it suitable for use in applicationswhere semi-conductor transistors are unsatisfactory.

One feature of the invention is that it comprises a first electrode, asecond electrode, a material in operative relatiOn with the electrodeswhich contains particles capable of migrating to one of the electrodesand effecting a change of charge therewith, and a third electrode foralfecting or controlling the migration of the particles. Another"feature is that the third electrode establishes the material or mediumused at an operative potential relative to one of the other electrodes.A further feature is that the first and second electrodes are closelyspaced or adjacent each other while the third or base electrode isrelatively remote therefrom. Another feature is that means are provided,in the material or medium surrounding the electrodes, which accept acharge from one of the first or second electrodes and deliver it to theother. And a further feature is that an ionizable medium is used and areversible electrochemical reaction occurs at the first electrode whichresults in a net change of charge with the medium, the ions or neutralatoms formed in this reaction migrating to the other electrode where areverse reaction occurs resulting in a change of charge with the secondelectrode; the net result is a transfer of charge from the firstelectrode to the second electrode with the rate of reaction at the firstelectrode, and thus the rate of charge transfer to the other electrode,being controlled by the potential of the third electrode.

Another feature is that the current flow in the system, from the firstelectrode to the second electrode, is independent of the potential ofthe second electrode and can be controlled by an external resistor so asto be substantially independent of temperature. And a further feature isthat the device may he used as a constant current source for a variableload.

Other features and advantages of the invention will be readily apparentfrom the specification and from the accompanying drawings, in which:

FIGURE 1 is a sectional view of an embodiment of the invention;

FIGURES 2a. and 2b are schematic diagrams of circuits showing the use oftwo different forms of the invention;

FIGURES 3, 4 and 5 are schematic diagrams of semiconductor transistoramplifiers utilizing the electrolytic transistor of this invention as abias current source;

FIGURE 6 is a schematic diagram of a circuit using an electrolytictransistor as a current amplifier;

FIGURE 7 is a schematic diagram of a modified form of the invention,having a fourth electrode;

FIGURE 8 is a sectional view of a modified form of the invention havinga series of alternate plates for the first and second electrodes;

FIGURE 9 is a sectional view of a modified form of the invention usingconcentric cylinders for the first and second electrodes;

FIGURE 10 is a diagram showing the rectification characteristic of thedevice;

FIGURE 11 is a diagram showing the transistor current characteristic ofthe device; and

FIGURE 12 is a diagram showing the output characteristic of the device.

In the embodiment of the invention shown diagrammatically in FIGURE 1, acontainer 2% has therein a first electrode 21, a second electrode 22 anda third electrode 23. Electrical connections are made to each of theseelectrodes 21, 22 and 23 by wires 24, 25 and 26, respectively. Thecontainer is filled with a suitable transfer material or medium 27.Preferably, in order to control the operation of the device moreaccurately, only one surface of each of the electrodes is in contactwith the medium 27; accordingly, the back face of the electrodes 21 and22 and the wires 24 and 25 are insulated from the medium 27 by suitablematerial 28 which should not react with the medium.

The material or medium 27 used in the device contains particles whichare capable of migrating through the medium and of effecting a change ofcharge with the electrodes. A good example of such a medium is anelectrolyte; that is a medium which contains ions capable of effecting achange of charge with one or more oi the electrodes under properconditions.

For example, as shown in FIGURE 2a, the first electrode 21 may be biasedpositively with respect to the base electrode 23 by a voltage sourceshown as a battery Evil. The ions in the medium or electrolyte arenormally in the reduced state and the desired oxidationreductionequilibrium condition may be maintained by a suitable choice of thematerial of the base electrode 23. Ignoring for the time the secondelectrode 22 and its associated circuit, a current will flow fromelectrode 21 through the material 27 to electrode 23, which current maybe controlled by rheostat 31. When a relatively low voltage is impressedbetween electrodes 21 and 23, the current which flows will be dependentmerely on the resistance of the material or medium 27. However, as thevoltage increases a series of reactions will occur result ing in asubstantially increased how of current through the cell. Depending ofcourse on the medium used, these reactions may be similar to thoseencountered in the process of electrolysis or electrodeposition. In thecircuit of FIGURE 2a for example the electrode 21 is positively biasedwith respect to electrode 23 and functions as an anode while electrode23 serves as the cathode. Ancther way of stating this is that anoxidation reaction takes place at electrode 21 while a reductionreaction takes place at electrode 23.

FIGURE 10 shows an operating curve 32 for this circuit, still ignoringthe effect of electrode 22 and its as sociated circuit. The portion ofthe curve 32a illustrates the relatively slow increase of current I asthe voltage, V, is increased below the potential sulficient to initiatethe electrochemical reactions referred to. The break, 32b, in the curveoccurs when the voltage, V, becomes suflicient to sustain the reaction.The current then increases rapidly, "320, with a relatively smallincremental increase of the voltage V. In the curve shown in FIG- URE10, the increase in current falls off in the area 32d when the supply ofcarriers to the electrode is limited by diffusion. If a more highlyconcentrated solution were used, this limiting effect would occur at ahigher current.

In the circuit shown in FIGURE 2b, the electrolyte is normally in theoxidized rather than the reduced state; the reactions discussed aboveare reversed as is the polarity of battery 39. Oxidation takes place atelectrode 23 and reduction at electrode 21.

When the electrode '22 and its associated circuit 33 are added, it hasbeen found that at least some of the current instead of flowing betweenelectrodes 21 and 23 flows from electrode 21 to 22, While the rate ofcurrent flow is still determined by the potential between electrodes 21and 23. If the electrode 22 is placed sufficiently close to theelectrode 21, substantially all the current will flow directly betweenelectrodes 21 and 22 rather than through electrode 23.

As this operation is analogous to that encountered in semi-conductortransistors, analogous terminology and current and voltage conventionhave been adopted. Electrode Zll will hereinafter be referred to as theemitter, 6, electrode 22 as the collector, c, and electrode 23 as thebase, b. Positive currents and potentials will be assumed as shown inFIGURE 2.4 and as specified in the book by Shockley, Electrons and Holesin Semi- Conductors, at page 36.

It is desirable, in order to minimize power loss in the device, that thebase-to-material or base-to-electrolyte resistance be as small aspracticable. One way of accomplishing this is shown in FIGURE 1 Wherethe base 23 is relatively large and has a large surface area in contactwith the material 27. The entire container 2% may be made the thirdelectrode if desired. The resistivity of the electrolyte should also below.

It has been found that the potential of the collector, V has, at leastwithin certain ranges, no effect on the collector cur-rent, I This isshown in FIGURE 12 Where the collector current, l is plotted as afunction of the collector voltage V for a fixed emitter voltage. Thestraight line portion of the curve, 34a indicates that the collectorcurrent I is independent of the collector voltage V through a fairlywide range. The portions of the curve 34b and 340, where the currentchanges markedly, occur when the voltage V exceeds the potentialnecessary to carry on the electrochemical reactions. Within the rangeshown however the collector current is dependent only on the emittervoltage, V. Thus, the voltage applied to the collector and accordinglythe load connected in the collector circuit may vary considerablywithout affecting the current flowing therethrough.

In one particular embodiment of the invention which has been operated,the casing 20 was made of Lucite, while the emitter 21 and collector 2.2were circular platinum discs. The base electrode 23 was formed by amercury pool in the bottom of the container. All me tallic parts whichwould come into contact with the solution, except for the faces of theemitter and collector, were coated with Lucite-acetone cement toinsulate them from the solution and to prevent undesired reactions.Polystyrene-CCL, cement might also "be used.

The solution used as a medium contained 0.25 M FeSO and 1.5 M HCl. Itwas found necessary to increase the emitter voltage, V,, to about 0.4volt to initiate the desired reaction. In this case, the ferrous ion,Fe++ is oxidized at the emitter, losing an electron, to form a ferricion, Fe+++. The oxidized ferric ions then migrate or travel by a processof diffusion to the collector 22 where the reverse reaction occurs, theferric ion gaining an electron, being reduced, to form a ferrous ion.Thus, a flow of current is established between the emitter and thecollector.

The base electrode 23 establishes the potential of the medium orelectrolyte 27 and effectively controls the flow of current.Technically, the potential difierencebetween the emitter 21 and the base23, V determines the rate of the electrochemical reaction at theemitter, and the flow of current, as shown in FIGURE 10. How ever, assubstantially all of the ions which are oxidized at the emitter migratedirectly to the collector, the potential of the base 23, by controllingthe rate of creation of oxidized ions, will hereinafter be said toaffect or control the migration of the ions or particles, in the senseof the quantity migrating to the other electrode, since this is for allpractical purposes a direct function of their rate of creation.

The hydrochloric acid used in this solution performs Several functions.First, a number of the Clanions react with the mercury pool forming thebase 23 to provide a thin layer of mercurous chloride, Hg Cl Thiscalomel electrode provides a low electrode-to-medium resistance andhelps to maintain the electrolyte in the reduced state. The acidicsolution also results in an improved conductivity and prevents ironhydroxides from precipitating out of the solution.

Another solution which has been used consists of l M NaCl and 0.2 M HCl.With this solution, the reactions are based on the chloride-chlorinecouple. The chloride ion, Cl, is oxidized at the emitter to formchlorine, at least part of which is reduced at the collector. When largecurrents are passed through the electrolyte, some of the chlorinemolecules form a gas given off as bubbles at the emitter so that thereaction is not completely reversible.

The bromide-bromine couple has also been studied and has been found tooperate successfully. No gas evolution was observed.

It is desirable, of course, to use an electrolyte in which the reactionsare reversible rather than one in which a gas is given off or a soliddeposited to prevent deterioration and possible exhaustion of the cell.Thus, it is more desirable to use the ferrous-ferric or bromide-brominesystems rather than the chloride-chlorine system as the first mentionedreactions are reversible.

The operation of both mediums which have been described involves anoxidation reaction at the emitter, 21, and accordingly the emitter mustbe biased positively with respect to the base 23 or medium 27, FIGURE2a. If the analogy to semi-conductor transistors is extended, thisdevice corresponds to a pup junction transistor. An electrolytictransistor corresponding to an npn junction transistor may be providedby using a medium containing a salt which has a positive ion that ispredominately in the oxidized state, for example, soluble salts of V+++.With a medium of this type, the emitter 21 would be biased negativelywith respect to the base 23 as shown in FIGURE 2b; the carrier ionswould be reduced at the emitter, each receiving an extra electron, andthen migrate by diffusion to the collector where they would be oxidizedto their former state, giving up the electron. Again, the potential ofthe base controls the rate of creation of reduced ions at the emitterand hereinafter will be said to affect or control the migration thereof.

It appears that the predominant state of, or equilibrium condition for,the ions in solution (i.e., reduced or oxidized) is primarily a functionof two properties of the cell; the oxidation-reduction potential of theion couple used, and the oxidation-reduction potential of the base orreference electrode used. It is my belief that if theoxidation-reduction potential of the base is more positive than that ofthe ion couple in the medium, the ions will tend to be predominately inthe reduced state when the system is in equilibrium. For example, if acalomel (Hg CI base electrode is used with a ferrous-ferric ion couple,the ions will tend to be in the reduced (Fe++) state as theoxidation-reduction potential of the calomel base is 0.270 volt and thatof the ferrous-ferric couple is 0.77 volt. On the other hand, if theoxidation-reduction potential of the base is more negative than theoxidation-reduction potential of the ion couple, the ions in solutionwill tend to the oxidized state. For example, if a solution containingvanadium ions (the V++ -V+ oxidation-reduction potential is 0.20 volt)is used with a calornel base electrode, the ions in solution will bepredominately oxidized.

The mobility of the ions in the solution is relatively poor as comparedwith the mobility of electrons or holes in semi-conductors. The devicewill not respond to frequencies much above 1 c.p.s., the cut-offdepending on the mobilities and on electrode spacing. Thischaracteristic gives rise to several possible uses for the device.

Broadly, the electrolytic transistor can be used as a constant currentsource for a variable load. In the circuits shown in FIGURES 2a and 2b,the collector current, I flows through a load illustrated as atwo-terminal network 33. The magnitude of this current is determined bythe voltage between the emitter 21 and the base 23 and is, withinlimits, completely independent of the magnitude of the load 33.

One specific example of such a load is a semi-conductor transistor. Intransistor circuits, it is necessary to bias at least one of thetransistor elements by a current of the proper polarity in order thatthe transistor will operate in the proper range. Particularly with thejunction transistor, the DC. resistance between elements varies rathermarkedly with temperature changes; sometimes as much as per degreecentigrade. It is diflicult with ordinary power supplies to provide aconstant current through a resistance which varies so greatly. Theelectrolytic transistor is particularly well adapted for use as atransistor bias source as it has a constant output with a varying load,it can be designed to have extremely low impedance to alternatingcurrents, and to have the bias current relatively unaffected bytemperature changes.

FIGURE 3 shows an electrolytic transistor 35, of the same type shown inFIGURE 2a, used as a bias source for an npn semi-conductor transistoramplifier 36 connected for grounded base operation. The bias current iscontrolled by the battery 37 and rheostat 38 in the circuit of theemitter of the electrolytic transistor 35. The base 40 of theelectrolytic transistor is connected to the emitter 41 of thesemi-conductor transistor, while the collector 42 of the electrolytictransistor is connected to the base 43 of the semi-conductor transistor.The signal to be amplified may be applied to the transformer 44 in thecircuit of the emitter of the semi-conductor transistor while the outputof the stage may be developed across resistor 45 in the circuit of thecollector 46 of the semiconductor transistor.

FIGURE 4 shows a similar arrangement with a pup semi-conductortransistor, 47. Here the collector 42 of the electrolytic transistor isconnected to the emitter 48 of the semi-conductor transistor while thebase 40 of the electrolytic transistor is connected to the base 49 ofthe semi-conductor transistor. Again the bias current is controlled bypotentiometer 38. An input signal may be coupled to the amplifierthrough transformer 44 and the output signal is developed across loadresistor 45.

FIGURE 5 shows another modification in which an npn semi-conductortransistor 50 is connected for grounded emitter operation. Here, thebase 40 of the electrolytic transistor 35 is connected to the emitter 51of the semiconductor transistor, while the collector 42 of theelectrolytic transistor is connected to ground 52. A signal may be fedto the amplifier between terminals 53, connected to base 54 of thesemi-conductor transistor and terminal 55, connected to ground. Theoutput of the stage is developed across load resistor 45 in the circuitof the collector 56 of the semi-conductor transistor. Again, the biascurrent is controlled by rheostat 38 in the emitter circuit of theelectrolytic transistor.

FIGURE 6 shows the electrolytic transistor used as a current amplifier.Here again, the electrolytic transistor is of the pnp type shown inFIGURE 20: with the emitter 61 positively biased. A current to beamplified may be connected between terminals 62 and 63 in the circuit ofthe base 64. The amplified output will appear in the load 65 connectedin the circuit of the collector 66.

FIGURE 7 again shows an electrolytic transistor of the type shown inFIGURE 2a, with the addition of a fourth electrode, a second base, 70.This electrode 70 is established at a different potential from the base23 by a battery 71, in this case making electrode 70 more positive thanbase 23. An electrostatic field will be set up between electrode '70 andelectrode 23, with electrode 70 being more positive than electrode 23.As the charge carrying particles in this embodiment of the invention arepositively charged, the electric field between electrodes 70 and 23 willcause the particles to concentrate in that portion of the mediumrelatively adjacent electrode 23, resulting in a decreased resistancebetween the base 23 and the medium or electrolyte 27.

FIGURE 8 shows a modified arrangement of the emitter and collectorelectrodes. As shown here the emitter comprises three physically spacedbut electrically connected plates 21 which are sandwiched between fourlarger, electrically connected plates 22 forming the collector. Thecollector plates 22' are substantially larger than the emitter plates 21and this together with the sandwiched arrangement insures thatsubstantially all the charged particles leaving the emitter will migrateor diffuse to the collector.

Another arrangement of the emitter and collector electrodes is shown inFIGURE 9 where the emitter is a single cylinder El and the collectorcomprises a pair of cylinders 22" one inside and the other outside theemitter. Again, practically all charged particles leaving the emitterwill migrate to the collector.

This application constitutes a continuation of my application Serial No.359,014 filed June 2, 1953, and now abandoned.

While I have shown and described certain embodiments of my invention, itis to be understood that it is capable of many modifications. Changestherefore, in the con- Stl'llCllOIl and arrangement may be made withoutdeparting from the spirit and scope of the invention as disclosed in theappended claims.

Having now described the invention, What is claimed is:

1. An electrical system of the character described comprising: a devicehaving a first plate-like electrode, a second plate-like electrodeadjacent and in close proximity thereto While substantially uniformlyspaced therefrom, a medium containing ions in operative relation withsaid electrodes, and a base for establishing said medium at an operativepotential; means for biasing said first electrode with respect to saidbase for causing a change in charge of ions at that electrode, said ionsbeing capable of migrating to said other electrode and effecting achange in charge therewith, the electrode base potential controlling themigration of said ions; and a transistor having a plurality of elements,the circuit of at least one of said elements being connected in serieswith said second electrode and base for biasing said transistor.

2. An electrical system of the character described, comprising: a devicehaving a substantially plate-like first electrode, a substantiallyplate-like second electrode of substantially like size positionedadjacent and parallel thereto, a medium containing ions in operativerelation with said electrodes, and a base for establishing said mediumat an operative potential; a source of direct current potentialconnected in series with a variable resistance between said firstelectrode and base for bias ing said first electrode with respect to thebase to cause a change in charge of ions at the first electrode, saidions being capable of migrating to said second electrode and affecting achange in charge therewith, the first electrodebase potentialcontrolling the migration of said ions; and a transistor having aplurality of elements, the circuit of at least one of said elementsbeing connected in series With said second electrode and base forbiasing said transistor.

References Cited in the file of this patent UNITED STATES PATENTS1,409,383 Lane Mar. 14, 1922 1,439,526 Mershon Dec. 19, 1922 1,497,430Chubb June 10, 1924 1,877,140 Lilienfeld Sept, 13, 1932 8 LilienfeldMar. 7, 1933 Hammond Aug. 29, 1933 Mershon Feb. 27, 1934 Van Geel June18, 1935 Lilienfeld Feb. 19, 1952 Trent Ian. 12, 1954 Root July 27, 1954FOREIGN PATENTS Germany Oct. 29, 1919 France Feb. 12, 1925

